1. Field of the Invention
This invention relates generally to a reactor assembly, and more particularly to an overrunning brake, sometimes called a one-way brake, installed in the reactor assembly of a torque converter for use in a motor vehicle.
2. Description of the Prior Art
A torque converter is a hydrodynamic drive unit that transmits rotary power and has capacity to amplify torque. A torque converter includes an impeller, stator or reactor, and turbine, all of which are bladed wheels, enclosed within a toroidal cover filled with hydraulic fluid, such as automatic transmission fluid. The stator, located in a fluid path between the exit of the turbine and the inlet of the impeller, redirects fluid onto the impeller, thereby amplifying torque. When the torque converter overruns, it functions as a fluid coupling without amplifying torque.
When used in an automatic transmission for a vehicle, a torque converter includes a one-way brake (OWB) to react torque in the reactor during torque multiplication while the vehicle is accelerating at low speed. The OWB allows the reactor to spin freely, i.e., to overrun, when the vehicle is at constant speed and coasting. Allowing the reactor to spin freely while coasting reduces drag.
A conventional OWB includes at least three major components: steel outer and inner races, and locking elements, which are rollers or sprags located in an annular space between the races. The inner race transfers torque though splines onto a stator shaft, which is fixed against rotation. The outer race is pressed into the reactor, which is usually formed of aluminum or plastic.
The steel of the races and locking elements is of high grade due to the large magnitude of material stresses produced during operation. The races also required numerous machining operations, including drilling lubrication holes, rough and finish turning (generally all surfaces are turned), grinding and polishing for finish and tolerance, and broaching. The number of parts of a conventional roller or sprag OWB further increases their cost and complexity of manufacture.